Show and Tell - let us know what you're doing!

[Neale]

The title comes from a regular feature of my model engineering club where members can show projects in progress or finished. I'm posting here because I made passing reference to one of my projects in another thread. Someone asked me about it but I didn't want to clutter up that thread with that info.

I have to start by saying that I almost never make reference to work I do on my machine as very little of what I do would be of interest to others. However, it occurs to me that it might encourage other people a bit to know that a CNC router or similar isn't always about glamorous, flashy, bits of work. They are great, of course, but the bulk of the jobs I do with mine are much more mundane - but do you know? It's really useful to have a machine to help you do the boring, ordinary, stuff as well as the odd "good enough to put on the wall" projects. In the same way that I posted about my router - it looks like a crock of s**t but it works - it might help others understand just what machines like this can do and I'm all for encouraging people to jump in at the deep end.

Anyway, first project 'cos that's the one I was asked about is a wooden clock. Hands up on this one - I bought the design from someone else as the requirement arrived in the workshop a couple of weeks before Christmas and there was not time to design/develop something of my own. The design I bought was this one, one of a range of clocks from this designer. Again, because of time constraints I bought the high-grade plywood and hardware fittings kit from the same guy, although there is nothing particularly exotic about any of it and I have even found at least one source of the "aircraft-grade" plywood not too far from me. I bought the design as a set of DXF files for all the CNC-cut components, loaded them into Vectric Vcarve (not Fusion 360 this time as it is all pretty straightforward 2.5D toolpath stuff) and generated gcode for my machine, I had already bought a couple of brand new cutters especially for it to try to avoid any tearing or splintering on the ply, and in fact this stuff machined really well. Even then I made another little whoopsy in the CAM phase. I watched the machine start cutting pieces from the first panel and though to myself, "that seems to be going quite fast." Then I looked at the Mach3 screen - target feed rate was 60000mm/min. I had overlooked the fact that Vcarve, when you are setting up feed rates, has a drop down box for units. I had not noticed that this defaulted to mm/sec - and I had set it to 1000. Very conservative as I wasn't sure how this stuff would cut, especially with a lot of detail for things like gear teeth - but in fact it topped out at my machine's limit of 5000mm/min and didn't bat a eyelid. So, I learnt something there.

Cutting the clock parts is actually quite quick. I won't mention the fact that I carefully set the tool to one corner of the work to work coordinate zero but forgot to then hit the zero axis buttons on the Mach3 screen. Whoops - I wasn't going to mention that... Anyway, I found some lesser quality ply in the workshop to make a replacement of the gear wheel that was spoiled but took the opportunity to modify the design slightly so that the spokes are actually in the form of my grandson's initial. Nice to have personalised it.

Assembly takes rather more time - although a second one would go faster. Actually setting up. tweaking, adjusting, etc, took quite a long time. It was probably nearly two weeks before I had it running reliably and keeping fair time (it gains around 3mins per day, which is probably about as good as technology like this will get - if I want better I buy a quartz clock from a market stall for a couple of quid). Clocks are very sensitive to friction and getting the bearings just right, adjusting the pallet shape where the pallets pick up the teeth of the escape wheel, etc, took time. In the end I actually read up on the characteristics of this kind of escapement to better understand just how to adjust it, but it runs pretty well now.

Just to prove that it does exist and run (and you can tell it's mine by looking very carefully for the wheel with the initials as spokes!) It's fixed to a temporary board just so that I could hang it on a door - in the first couple of weeks it was up and down on a regular basis for adjusting. Sorry about the background noise on the video clip. Other people put all sorts of different background music on (which I have to admit often has me reaching for the mute button...) but this background was the television and completely accidental Your turn to reach for the mute button, guys!

My wife likes it enough that I shall be building at least one more, the next one having a bit more fancy wood and some nice engraving. That will be a lot easier now I know (more or less...) what I'm doing.